@Fourjets Here are some details about our Exuma trip that might help. Some of this might be posted throughout the thread but I'm to lazy to look for it.
Fuel - average was 2.5 mpg at roughly $4 to $4.50 per gallon. The rough number I use is whatever the fuel cost is in Florida (not marina gas) add $2 to $2.50 for the cost in the Bahamas.
Daily mileage - It all depends on the sea conditions and your travel/exploring plans.
Our travels
Day 1 - Fort Lauderdale to Bimini (cleared customs) to Chub Cay - 150 miles. We were hoping to make it to Nassau (190 total miles) but Chub Cay Marina wasn't pumping fuel until the morning.
Day 2 - Chub Cay to Nassau - 40 miles. Met up with friends and family that flew into Nassau and spent the night
Day 3 - Nassau to Staniel Cay, Exuma - 90 miles, final destination. Boats/skis stayed at Staniel Cay Yacht Club and we rented houses about 1/2 mile away
Day 4, 5, 6, & 7 - exploring north and south of Staniel Cay - guess we but probably traveled 200 to 300 miles
Day 8 - Staniel Cay to Nassau to Chub Cay to Bimini - 220 miles
Day 9 - hung out and explored with our fellow jetboaters in and around Bimini
Day 10 - Bimini to Fort Lauderdale - 60 miles
Travel speed is a big determining factor in how far you can go. Make sure the group you are with will travel at the same speed. A slow boat can really put a damper on your plans.
As for details on where we stayed, none of the places we stayed were spectacular enough to recommend. Chub Cay for instance, if you get stuck there, there is only one place to stay. Look at Nassau you will find plenty of places to stay, we stayed at a place on the east end of Paradise Island. Next time, I would look into a place in Palm Cay, this is location of the marina we used to fuel up going and coming. In Staniel Cay there are not many options, the size of your group will dictate where you might stay.
I don't have the details right now on the all the costs but my rough memory has the total cost for the wife and I at between $5000 and $6000.
There are a lot of variables to determine how much your trip will cost; fuel, lodging, slip rental, food, etc and don't forget about boat upgrades and safety equipment.
Hope this helps you get started in planning your adventure.